package net.neoremind.mycode.argorithm.leetcode;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import org.junit.Test;

/**
 * Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.
 * <p>
 * <p>
 * OJ's undirected graph serialization:
 * Nodes are labeled uniquely.
 * <p>
 * We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.
 * As an example, consider the serialized graph {0,1,2#1,2#2,2}.
 * <p>
 * The graph has a total of three nodes, and therefore contains three parts as separated by #.
 * <p>
 * First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
 * Second node is labeled as 1. Connect node 1 to node 2.
 * Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.
 * Visually, the graph looks like the following:
 * <pre>
 *   1
 *  / \
 * /   \
 * 0 --- 2
 *      / \
 *      \_/
 * </pre>
 * <p>
 * https://leetcode.com/problems/clone-graph/
 * <p>
 * 比较绕，难度中等
 *
 * @author zhangxu
 */
public class CloneGraph {

    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if (node == null) {
            return null;
        }

        UndirectedGraphNode newNode = new UndirectedGraphNode(node.label); //new node for return
        HashMap<Integer, UndirectedGraphNode> map = new HashMap(); //store visited nodes

        map.put(newNode.label, newNode); //add first node to HashMap

        LinkedList<UndirectedGraphNode> queue = new LinkedList(); //to store **original** nodes need to be visited
        queue.add(node); //add first **original** node to queue

        while (!queue.isEmpty()) { //if more nodes need to be visited
            UndirectedGraphNode n = queue.pop(); //search first node in the queue
            for (UndirectedGraphNode neighbor : n.neighbors) {
                if (!map.containsKey(neighbor.label)) { //add to map and queue if this node hasn't been searched before
                    map.put(neighbor.label, new UndirectedGraphNode(neighbor.label));
                    queue.add(neighbor);
                }
                map.get(n.label).neighbors.add(map.get(neighbor.label)); //add neighbor to new created nodes
            }
        }

        return newNode;
    }

    @Test
    public void test() {
        UndirectedGraphNode n0 = new UndirectedGraphNode(0);
        UndirectedGraphNode n1 = new UndirectedGraphNode(1);
        UndirectedGraphNode n2 = new UndirectedGraphNode(2);
        n0.neighbors.add(n1);
        n0.neighbors.add(n2);
        n1.neighbors.add(n0);
        n1.neighbors.add(n2);
        n2.neighbors.add(n0);
        n2.neighbors.add(n1);
        n2.neighbors.add(n2);

        UndirectedGraphNode r = cloneGraph(n0);
        System.out.println(r);
    }

    class UndirectedGraphNode {
        int label;
        List<UndirectedGraphNode> neighbors;

        UndirectedGraphNode(int x) {
            label = x;
            neighbors = new ArrayList<UndirectedGraphNode>();
        }

        @Override
        public String toString() {
            return label + "";
        }
    }

}
